The present invention relates to a vehicle door such as a front door, rear door, and a tail door.
To improve the fuel economy of a vehicle, reduction in weigh of the vehicle is an effective measure. This is because weight reduction of a vehicle reduces the energy required for driving the vehicle. Methods for reducing the weight of a vehicle include reduction in weight of materials, reduction in size and weight of individual parts, and reduction in the number of parts by improvement of function.
For example, Japanese Laid-Open Patent Publication No. 2004-255906 discloses a technology for reducing the weight of a vehicle component, or a vehicle door having a door main body and window glass. The vehicle door has an iron pipe between the inner panel and the outer panel of the door main body. Shock absorbing material is provided in occupant protection areas above and below the iron pipe. The shock absorbing material is formed of a honeycomb structural body and a pair of planer members attached to both sides of the honeycomb structural body. The weight of the vehicle door is reduced by the use of the honeycomb structural body as a part of the shock absorbing material. When an impact is applied to the vehicle door, the shock absorbing material is deformed to absorb the impact.
In addition to demands for reduction in weight, there are demands for higher strength of vehicle doors. However, the vehicle door disclosed in the above publication is formed simply by constructing a part of the door main body with shock absorbing material. Therefore, the weight of the entire vehicle door including the window glass is not sufficiently reduced. Further, in the vehicle door of the publication, the honeycomb structural body is used primarily for improving the shock absorbing performance, and the improvement of the strength is not fully considered.